Fuel cooler with lamellar inner structures for connecting to an air-conditioning system of a vehicle

ABSTRACT

A fuel cooler with lamellar inner structures for connecting to an air-conditioning system of a vehicle includes an outer housing having outer connections connected to an outer supply pipe and an outer discharge pipe for a first fluid with the outer connections being integrated into walls of the outer housing in a diagonally mismatched arrangement. An inner conduit cell, surrounded by the outer housing, has an inner supply pipe and an inner discharge pipe for a second fluid passing through the inner conduit cell, which includes lamellas oriented parallel to a direction of flow of the second fluid, with the first fluid coming into contact with an outer contact surface of the inner conduit cell prior to exiting the outer housing for creating a heat exchange between, and without a mixing of, the two fluids, which are fuel and a coolant.

BACKGROUND OF THE INVENTION Technical Field of the Invention

The invention relates to a vehicle with combustion engine, fuel tank andair conditioner and a heat exchanger connected with the fuel pipe thatis integrated into the coolant circulation system of the airconditioner. The fuel cooling unit comprises an outer housing withconnection for feeder and discharge pipes and a pipe running inside theouter housing.

DESCRIPTION OF THE PRIOR ART

Fuel may heat upon in a vehicle for various reasons. The fuel in thetank may heat up due to the heat produced by solar radiation or the fuelin the fuel pipes may heat up due to the radiation heat coming fromdrive sites and the radiation heat produced in the exhaust gas facility.The heated up fuel, steam bubble may develop in the fuel which interruptthe smooth operation of the engine. The technical term used for theselittle interruptions is “misfire”. This problem particularly occurs whendriving at high speeds and in case of compressor and turbo engines witha high consumption. That is why engineers have been making effort todevelop devices for cooling the fuel for long time. This is reflected bythe large number of patents and disclosure documents describing fuelcooling units.

When taking a closer look at these documents that deal with the interiordesign of the fuel cooling unit it becomes apparent that these devicesgenerally refer to improvement inventions aimed at increasing thecooling effect which is mainly determined by the size of the heattransmission surface and the distribution of the coolant. That is whydesign modification efforts have been made in order to enlarge this heattransmission surface to enhance distribution of coolant in the majorityof devices designed as fluid-heat exchangers. The efforts made toimprove the coolant distribution aim at flushing the fuel-carrying pipeswith coolant homogenously. The following is a short description of thedocuments to be regarded among state-of-the-art papers.

The device described in DE 34 40 060 refers to a fuel cooling unit wherethe fuel to be cooled is pumped through a curled hose which has theshape of a coil. This curled hose is radially supported by the innerwall of the radiator housing, while the cylindrical housing is flushedwith coolant in axial direction. Due to restricted space available andbending problems, the coil has been made in 5 different individualpieces for this device. This device shows to major disadvantages: lowcooling performance and the difficult manufacturing process of the coil.

Document DE 41 10 264 A1 outlines a recommendation for improvement ofthe cooling performance of the device described in DE 34 40 060 A1: Inorder to avoid the effect that the cooling performance stays constantdespite higher coolant throughput or may even be reduced, the corecross-section of the fuel-carrying coil was filled with a body on whichthe fluid is flowing. This flow body was designed as twist sheet in thiscase which can be inserted between two adjoining windings of the curledhose coil. The contours of this twist sheet redefine the flowingcross-section going through the coil inside the housing and lead to amore homogenous flushing of the fuel-carrying coil.

Document DE 37 40 811 A1 recommends a spherical surface type housinginstead of the cylindrical basic shape of the fuel cooling unit used sofar which is fitted with a spiral with the fuel to be cooled in aposition that allows the windings of the spiral to be positioneddiagonally to the coolant stream. This subjects the stream of thecoolant to new thermal start-up procedures at each winding which leadsto turbulent currents which ensure good flushing of the fuel-carryingpipes.

Document DE 44 37 167 A1 describes a fuel cooling unit which shows amuch larger heat transmission surface. Cylindrical bellows are used inthis device as the major component of the fuel cooling unit between theends of a fuel-feeding and a fuel-discharging pipe. The fuel coolingunit is equipped with a housing that consists of a hollow cylindersection with fuel feeding and fuel-discharging pipe and a lateral edge.ring-waved bellows are positioned inside the housing cover in a radialdistance which is fixed on a hollow cylindrical guidance body of thesame length with no play.

The guidance body is equipped with a wall in the current cross-sectionthat is inclined towards the current direction which ranges over theentire length of the guidance body which is connected in one piece withits front and rear end as related to the current direction of thecoolant with the adjoining end of the guidance body. Openings arelocated at both sides of the wall in the hollow cylindrical cover of theguidance body which are positioned in diametrically opposed to eachother. The openings positioned in parallel along the axle of the coverline of the guidance body terminate on the outside of the guidance bodyin the flanks of the all-round bellows curves open towards the insidewhile fuel is being transported in the flanks of the bellows curves opentowards the outside in the opposite direction. The fuel is permanentlyforced alongside the bellows curves open towards the inside through thewall positioned in an inclined position towards the current direction ofthe fuel so that on such enlarged heat transmission surface there can bean optimal heat exchange with the fuel streaming on the other side ofthe flanks.

The complicated technical design and the necessity for exact fixation ofthe guidance element which is a material precondition for a correct feedof fuel or coolant to the individual bellows curves are disadvantages ofthis device. Furthermore, no large throughput rates are possible due tothe small cross-section of the bellows curves

Connection of a fuel cooling unit to the coolant circulation system ofthe air condition is already state-of-the-art: Document DE 37 25 664 A1describes the installation of a fuel cooling unit not further describedregarding its inner design into the coolant circulation before theevaporator, while document DE 33 30 250 A provides for the installationof a fuel cooling unit not further described in more detail, either,between evaporator and compressor.

SUMMARY OF THE INVENTION

The invention is associated with the problem of designing a fuel coolingunit to be installed into vehicles with air conditioning, which offers aheat exchange surface of sufficient size and of a simple design in orderto ensure a homogenous distribution of the coolant, so that a high fuelthroughput rate can be guaranteed at high speeds.

In order to solve this task, the invention describes a fuel cooling unitwhere

-   -   the pipe (3) located inside the outer housing is widened to a        cell and where    -   the cell created by widening the pipe (3) is equipped with        lamellas (5) at the inside in parallel position to the current        direction.

The core piece of the invention is based on the idea that a contactsurface for heat exchange between fuel and coolant is created where theareas next to the contact surface are designed to guarantee quicker heatexchange. That is why two housings were fit into one another andadditionally, a network structure was integrated in the interior of theinner housing consisting of lamellas with cross-links. The cross-linksbetween the lamellas positioned in current direction provide for a quickheat exchange between the individual lamellas at the one hand and ensurea homogenous mix of the coolant in the relevant clearance spaces. Thisconstant mixing of the coolant is another important precondition for aquick heat exchange.

The advantages of the fuel cooling unit as outlined in this inventionare numerous. Cooling of the fuel prevents the development of steambubbles and evaporation of fuel additives. This supports optimalcombustion of the fuel with minimum emission. This results in a smoothidle operation and, in particular, improved performance of engines withhigher fuel consumption. Higher engine performance and better fueleconomy could be proved by measurements. Furthermore, the heat exchangeras outlined in the invention supports trouble-free new start of engineswhich are warm from operation. Due to the fact that cooled fuel can becompressed more easily, the strongest effect of the fuel cooling unit asoutlined in the invention is achieved for compressor and turbo engines.The lamella-type structures inside the fuel cooling unit accelerate heattransportation to both sides of the heat transmission surface andstabilise the outer housing and the inner cells whenever higherpressures occur.

There are two designs available for the fuel cooling unit as outlined inthe invention. The outer housing may be integrated into the fuel pipebetween the fuel tank and fuel pump or into the coolant circulationsystem of the air conditioner. If the first option is chosen, i.e.,installation in the outer housing of the fuel pipe, the inner cell willbe integrated into the coolant circulation system of the airconditioner. In case the second design is preferred, it might bepossible to integrate the inner cell into the fuel pipe and to connectthe outer housing to the coolant circulation system of the airconditioner. (The first preferred option was used for test measurementsperformed so far, i.e. the outer housing was integrated into the fuelpipe between the fuel tank and fuel pump, while the inner cell wasconnected to the coolant circulation of the air conditioner.)

Based on another invention feature, the fuel cooling unit can also beintegrated into the coolant circulation system before, or after, theevaporator of the air conditioner.

If the fuel cooling unit is integrated into the coolant circulationsystem after the evaporator, this will result in a relatively limitedcooling of the fuel. However, cooling performance will be higher, if thefuel cooling unit is integrated into the cooling circulation systembefore the evaporator.

The invention further provides that the current direction of the fuelinside the fuel cooling unit is moving in the opposite direction of thecurrent direction of the coolant. The opposite current direction of fueland coolant will beneficially result in an improved cooling performance.

Another material feature of the invention is that the sections notfilled by the inner cell inside the outer housing are also equipped withlamellas which are positioned in parallel towards the current directionand which in a specially preferred design are linked to a networkstructure like the lamellas inside the inner cell by additionalcross-links. The network structure in both hollow bodies provides for anacceleration of the heat transport to the lamellas located further awayfrom the border surface and results in a swirling of the fluids furtheroptimizing heat transport and to a homogenous flushing of the bordersurface towards both sides.

Another particularly preferred design of the fuel cooling unit outlinedin the invention provides that the outer housing and the cell in theinterior consist of six side surfaces in vertical position to each othereach. The middle lines of the rectangular parallelepiped hollow bodiesmeet in the assembled fuel cooling unit. In this case the inner cell isshorter in longitudinal direction than the outer cell so that thereremains a clearance between the two hollow bodies which is filled byfuel and coolant in the operating condition.

Another preferred design of the fuel cooling unit outlined in theinvention provides that the outer height of the rectangularparallelepiped cell corresponds exactly with the inner height of theouter housing so that the inner cell is optimally fitted with its topand bottom side without any clearance in the outer housing. Since thetwo pipe connections of the outer housing are integrated into eachrespective wall of the top and bottom side of the housing in adiagonally mismatched position, the inner cell is flushed by fuel or bycoolant at least two long sides and at the two front sides in theoperating condition in this preferred design.

It corresponds to the idea of the invention that the components used todesign the outer housing and the inner cell and the lamellas and thecross-links inside both hollow bodies are made of a metal with highthermal conductivity such as aluminium or copper. When using aluminium,tungsten inert gas welding (wig welding) with a needle is used toconnect the components. This way the connections, which have differentsizes because of the various throughput levels, and the fine-steelcoated fuel hoses which also may have different diameters, can be fixed.The different connection sizes are adapted to each vehicle and enginevariant helping to achieve the best possible engine performance.

BRIEF DESCRIPTION OF THE DRAWING FIGS.

For further details and features of the invention, please refer to thefollowing descriptive part of the drawing. The drawing and thepertaining description are not designed to limit the invention, butshould render further detailed information.

DETAILED DESCRIPTION OF THE DRAWING FIGS.

FIG. 1 shows one of several possible designs of the fuel cooling unit asoutlined in the invention. Inner cell 3 is positioned inside outerhousing 1. Connections 4 a and 4 b belonging to inner cell leave housing1 on the front sides. Lamellas 5 positioned in current direction andcross-links not completely illustrated can be seen inside the innercell. The cross-links provide for a mixing of the fluids when flowingthrough the lamellas thereby supporting heat exchange.

The connections of the outer housing 2 a and 2 b are located indiagonally mismatched position on the two side surfaces of outer housing1. The space not filled by inner cell 3 inside outer housing 1 is notfilled with lamellas and respective cross-links in the exampleillustrated here. Of course, another design could be possible where thisclearance is filled with lamellas and cross-links like shown for innercell 3.

1. A fuel cooler with lamellar inner structures for connecting to anair-conditioning system of a vehicle, comprising: an outer housinghaving outer connections able to be connected to an outer supply pipeand an outer discharge pipe for a first fluid, said outer connectionsbeing intergrated into walls of said outer housing in a diagonallymismatched arrangement; and, an inner conduit cell surrounded by saidhousing and having an inner supply pipe and an inner discharge pipe fora second fluid passing through said inner conduit cell, said innerconduit cell having lamellas oriented parallel to a direction of flow ofsaid second fluid, with said first fluid coming into contact with anouter contact surface of said inner conduit cell prior to exiting saidouter housing for creating a heat exchange between, and without a mixingof, said first fluid and said second fluid.
 2. The fuel cooler withlarnellar inner structures for connecting to an air-conditioning systemof a vehicle according to claim 1, wherein said first fluid is a fueland said second fluid is a coolant.
 3. The fuel cooler with lamellarinner structures for connecting to an air-conditioning system of avehicle according to claim 1, wherein said first fluid is a coolant andsaid second fluid is a fuel.
 4. The fuel cooler with lamellar innerstructures for connecting to an air-conditioning system of a vehicleaccording to claim 1, wherein a direction of flow of said first fluidthrough said outer housing is opposite to the direction of flow of saidsecond fluid through said inner conduit cell.
 5. The fuel cooler withlamellar inner structures for connecting to an air-conditioning systemof a vehicle according to claim 1, further comprising additionallamellas within a portion of said outer housing not occupied by saidinner conduit cell, said additional lamellas being positioned paralleltoward a direction of flow of said first fluid through said outerhousing.
 6. The fuel cooler with lamellar inner structures forconnecting to an air-conditioning system of a vehicle according to claim1, wherein said inner conduit cell has a cuboid structure.
 7. The fuelcooler with lamellar inner structures for connecting to anair-conditioning system of a vehicle according to claim 1, wherein saidouter housing is made of a metal having a high thermal conductivity. 8.The fuel cooler with lamellar inner structures for connecting to anair-conditioning system of a vehicle according to claim 1, wherein saidinner conduit cell is made of a metal having a high thermalconductivity.
 9. The fuel cooler with lamellar inner structures forconnecting to an air-conditioning system of a vehicle according to claim1, wherein said lamellas of said inner conduit cell are made of a metalhaving a high thermal conductivity.
 10. The fuel cooler with lamellarinner structures for connecting to an air-conditioning system of avehicle according to claim 1, wherein said outer connections of saidouter housing include a first outer connection integrated into a topwall of said outer housing and a second outer connection integrated intoa bottom wall of said outer housing in said diagonally mismatchedarrangement.